Growth of a Feather 254 Horns of Stag 258 Skull of Babiroussa 262 Skull of Hippopotamus 265 Skull of Elephant 267 Growth of Hair 278 Section of Human Tooth 282 Garden Tulip 298 Germination of Earth-pea 300 Seed of Mangrove 303 Lace-fly and Eggs 312 Brachionus with Eggs 322 Pregnant Asplanchna 323 Hen's Egg 329 Gyroceras 371 [Greek: HO OMPHALOS.] I. THE CAUSE. "Is there not a cause?"--1 SAM. xvii. 29. An eminent philosopher has observed that "nothing can be more common or frequent than to appeal to the evidence of the senses as the most unerring test of physical effects. It is by the organs of sense, and by these alone, that we can acquire any knowledge of the qualities of external objects, and of their mutual effects when brought to act one upon another, whether mechanically, physically, or chemically; and it might, therefore, not unreasonably be supposed, that what is called the evidence of the senses must be admitted to be conclusive, as to all the phenomena developed by such reciprocal action. "Nevertheless, the fallacies are numberless into which those are led who take what they consider the immediate results of sensible impressions, without submitting them to the severe control and disciplined analysis of the understanding."[1]